Alloys of mercury



April 30, 1963 B-. F. FREEBERG 3,087,811

ALLOYS 0F MERCURY Filed Nov. 3, 1960 VARIATION OF THE FREEZING POINTWITH VARIATION .OF

THE THALLIUM CONCENTRATION I3 I4 I I5 I6 FIG.I

VARIATION OF THE FREEZING POINT WITI-I VARIATION OF THE INDIUMCONCENTRATION FIG-2 INVENTOR. BENJAMIN F. FREE BERG LIOQJMAA ATTO RN EYUnited States Patent 3,087,811 ALLOYS 0F MERCURY Benjamin F. Freeberg,Lombard, Ill., assignor to Vapor Corporation, a corporation of DelawareFiled Nov. 3, 1960, Ser. No. 66,979 3 Claims. (Cl. 75-169) The presentinvention relates to alloys and particularly to alloys for use inthermometers and thermostats of the liquid column type.

The alloy of the present invention embodies a three component amalgam ofindium, thallium, and mercury which remains in a liquid state atextremely low temperatures and at temperatures below those of mercuryalloys as heretofore known. The alloy is particularly suitable for useas the liquid medium in resistance devices, such as that disclosed in myU.S. Patent No. 2,906,981, and in thermostats such as is disclosed inPatent No. 2,596,825, issued to applicant and others. In this age ofouter space exploration it is necessary to provide thermostatic devicescapable of withstanding extremely low temperature which may beencountered in space or in low temperature environs wherein equipmentmay be stored.

The alloy herein disclosed has a freezing point of -82" F.

Accordingly, it is an object of my invention to provide a mercurycomposition which is susceptible to low freezing temperatures, retainingthe liquid properties of mercury at such lower temperatures.

It is a further object of my invention to provide a eutectic mercuryamalgam which may be used in connection with control equipment found inguided missiles, electronic signaling devices, outer space apparatus andaircraft generally, where extremely low temperatures may be encountered.

Another object of my invention is to provide an alloy for use inthermostats and thermometers which encounter temperatures of minuseighty degrees Fahrenheit (-80 F.) or lower.

It is a further object to provide a mercury composition which may besubjected to extremely low temperatures and which when brought to highertemperatures will retain its physical properties.

The characteristics of the alloy are demonstrated graphically whereinFIGURE 1 depicts the results in freezing point variation with thevariation of the thallium concentration; and

FIGURE 2 depicts the results in freezing point variation with variationof the indium concentration.

Mercury freezes at 40 F. and consequently its use in thermometers and inthermostats is limited to such sub-Zero temperature range. In certaintwo component eutectic compounds, the freezing point may be lowered to'-74 F. Such result is obtained with a mercurythallium amalgam, whereinthe thallium represents 8.75% by weight of the amalgam.

In the present invention, it has been discovered that the use of a threecomponent system will further reduce the freezing point. Such a eutecticis comprised of indium, thallium, and mercury resulting in an amalgamwhich freezes at -82 F.

The composition of this alloy is:

Percent Indium 16.0 Thallium 14.3

Mercury 69.7

lCe

A. Density, grams per cubic centimeter:

At F 11.723 At 0 F 11.797 At 50 F 11.842 B. Thermal coeflicient ofcubical expansion per degree F. From 0 F. to +80 F 78x10- From 50 F. to0 F 76x10" C. Specific resistance at 80 F., ohms per cm. 54.06 10 D.Dynamic viscosity, centiposes, at 68 F- 0.35990 E. Specific heat,calories per gram 0.356

In the preparation of the amalgam, the proper amounts of the indium andthallium are Weighed and dissolved in a weighed amount of mercury. Theresulting mixture is cooled to the eutectic temperature of 82 F. andfiltered to remove compositions, if any, outside the eutectic range.

The proportions of the indium concentration may be varied from 14.9% to16.6% with corresponding variation of the thallium content within onedegree of the prescribed eutectic temperature of 82 F. The results ofsuch variation of the concentration of indium relative to thallium andvice versa in terms of freezing point is shown in the attached graph.This data is depicted in the form of graphs shown in FIGURES 1 and 2wherein the upper curve presents the temperature at which crystalsstarts to separate. The lower curve presents the temperature at whichthe solidification is complete. The temperature corresponding to theareas between the curves embody a mixture of solid and liquid. Theportion of the curves below the dotted line show the allowablecomposition if a freezing point of 81 F. is allowed. This is 1 F. abovethe eutectic freezing point.

Certain other variations in the proportions of the elements present inthe alloy may be made without departing from the spirit of the inventionor the scope of the appended claims.

What I claim is:

1. A mercury alloy consisting of from 13.1% to 15.5% thallium, 16.0%indium and from 68.5% to 70.9% mercury.

2. A mercury alloy consisting of from 14.3% to 16.7% indium, 14.3%thallium and from 69% to 74% mercury.

3. A mercury alloy consisting of 69.7% mercury, 16.0% indium and 14.3%thallium to provide a eutectic, the freezing point of which is -82 -F.

References Cited in the file of this patent UNITED STATES PATENTS

3. A MERCURY ALLOW CONSISTING OOF 69.7% MERCURY, 16.0% INDIUM AND 14.3%THALLIUM TO PROVIDE A EUTECTIC, THE FREEZING POINT OF WHICH IS -82* F.